1. Field of the Invention
This invention relates to resin-treated sheet-like structures in which a disperse dye-colored polyester fiber is used and to a process for producing the same. In particular, it relates to resin-treated sheet-like structures excellent in the effect of preventing migration and sublimation of said disperse dye and a process for producing the same.
2. Description of the Prior Art
Polyester fibers are fibers having distinct advantages of which the easy care property is a typical example. However, the number of those resin-finished products which are on the market and in which polyester fibers are used, such as water vapor-permeable, waterproof cloths, coated cloths and laminated cloths, is very small. Nylon fiber-made cloths constitute the mainstream in this field. The reason why polyester fibers are not used in the resin-finished products mentioned above is that when such products are made by using polyester fibers, the disperse dyes used for coloring the polyester fibers migrate through the resin layer and stain other textile fabrics during storage and sewing thereof and clothings during wearing thereof. This is presumably because polyester fibers do not form' chemical bonds with disperse dyes while nylon fibers are colored and chemically bound with ionic dyes. Furthermore, studies by the present inventors have revealed that disperse dyes are closer in solubility parameter to resins used in resin finish treatment, such as polyurethanes, polyacrylic esters and polyvinyl chloride, than to polyesters and thus have greater affinity for resin layers than for polyesters. This is also a reason for the migration of disperse dyes.
Several attempts have indeed been made to prevent migration and sublimation of disperse dyes. For instance, as described in Japanese Patent Publication Kokai No. 59-82469, (Publication Date-May 12, 1984)an attempt consists in providing fibrous structures with a monomeric melamine compound, causing crosslinking by heating to thereby form a layer scarcely permeable to dyes and thus decrease the rate of dispersion of dyes, and, thereafter, coating the structures with a polyurethane, for instance. However, the melamine compound-derived film renders fibrous structures hard in feel and touch and, in addition, shows poor adhesion to resin layers. Furthermore, said melamine compound-derived film has a solubility parameter of 8-9.5 (cal/cm.sup.3).sup.1/2, which is almost equal to the solubility parameter of disperse dyes [8.3-9.7 (cal/cm.sup.3).sup.1/2 ], so that said film is not so effective in preventing dye migration and sublimation.
It is also conceivable to provide fibrous structures with a silicone emulsion or a fluorine derivative emulsion. However, to cover the fiber surface completely is difficult and the products have little advantages. The effect of preventing dye migration and sublimation is small and the adhesion between the coat layer and the resin layer is very poor.
As disclosed in Japanese Patent Publication Kokai No. 58-214587 (Publication Date-Dec, 13,1983), for instance, it is further conceivable to subject fibrous structures first to resin treatment and then to film formation treatment. However, the film formation is very difficult to realize by the conventional processes. The reason is as follows: In the conventional resin treatment processes, solventbased film forming compositions are mainly used and therefore the resin-treated surface is generally hydrophilic, so that aqueous emulsions in general use are repelled and cannot form films. Even when the use of a solvent-based resin composition is considered for achieving adhesion of the resin to the hydrophilic surface, the solvent must not dissolve the resin layer already formed while, if the solvent cannot swell the resin at all, adequate adhesion cannot be obtained. The solvent selection is thus very difficult. Therefore, a special pretreatment step is required and this makes the whole process complicated, and the adhesion is still unsatisfactory.
In Japanese Patent Publication Kokai No. 53-16085 (Publication Date-Feb 14,1978) and Japanese Patent Publication Kokai No. 53-8669 (Publication Date-Jan. 26, 1978), it is disclosed that, for preventing plasticizers contained in polyvinyl chloride resins from bleeding out, the resin surface should be coated with a compact polymer formed upon contacting a gaseous fluorocarbon or a gaseous organosilicon compound with an inert gas plasma. It is thus known to form a plasma-polymerized film on the polyvinyl chloride surface by plasma polymerization using low temperature plasma discharge. However, this technique is nothing but a technique to prevent plasticizer bleeding.
Furthermore, in Japanese Patent Publication Kokai No. 60-119273 (Publication Date-June 26, 1985) filing laid open after filing of the instant application, there are described waterproof cloths and a process for producing the same which comprises causing a silane compound and/or a fluorine compound to adhere to a disperse dye-colored polyester-based cloth, causing crosslinking by means of a low temperature plasma and then coating the cloth surface with a resin.
In their study, which has led to the present invention, the present inventors checked this technique and found that said technique is still unsatisfactory in the effect of preventing migration of and staining with disperse dyes and further that the adhesion of resins for coating is poor.
The results obtained by the present inventors using the above technique are as follows:
At first, the present inventors, who found that crosslinking occurs on the fiber surface upon low temperature plasma treatment, subjected a disperse dye-colored polyester cloth to low temperature plasma treatment in argon, carbon monoxide, and so forth and then, after crosslinking on the surface of fibers occurring on the uppermost surface of the cloth, to coating treatment with a resin. With the cloth thus obtained, the effect of preventing dye migration could be seen to some extent when the coated cloth was in a dry condition whereas, when the coated cloth was immersed in water, then wrung to a certain moisture content and maintained in such wet condition, no migration preventing effect was observed at all. It was found that this is due to the fact that crosslinking occurs upon low temperature plasma treatment only on limited sites on the surface of fibers occurring on the uppermost surface of the cloth, so that dyes can migrate into the coating layer via uncrosslinked portions with the assistance of water which serves as a medium or vehicle when the test is carried out in a wet condition.
Then, the present inventors evaluated various compounds for adequacy of using them in causing them to adhere to polyester-based cloths, effecting crosslinking by means of a low temperature plasma and then carrying out resin coating treatment, as disclosed in the above-cited publication. While silicon compounds and fluorine compounds can be expected to be more or less effective in preventing dye migration even when such low temperature plasma treatment is omitted, it was found that when the cloths with said silicon compounds or fluorine compounds adhering thereto are coated with resins, the resin adhesion is very poor, uniform coating cannot be attained, the coats are readily peelable and the products therefore become valueless.
It was found that, in low temperature plasma treatment using silicon compounds or fluorine compounds, etching readily proceeds and effective crosslinking hardly proceeds although crosslinking may take place partly, and that, in testing in a wet condition, the effect of preventing dye migration is still poor because crosslinking sites are limited to the surface of fibers occurring on the uppermost cloth surface, although testing in a dry condition reveals a certain extent of effectiveness.
In both the above cases, uniform film formation on the fiber surface can be achieved only by increasing the amount of silicon compounds or fluorine compounds to a considerable level. In small amounts, the polyester fiber surface remains uncovered, so that no dye migration preventing effect can be produced. In large amounts, on the other hand, cloths become hard in feel and touch and at the same time the water vapor permeability required of the cloths is reduced. Furthermore, the low temperature plasma treatment itself cannot improve the adhesion between the plasma-treated surface and the resin for coating, so that nonuniform coating results and peeling readily occurs at the interface between the silicon or fluorine compound and the coating resin layer. Therefore, the products obtained are unsatisfactory ones.